London (March 2002): Women infected with the common sexually transmitted human papilloma virus
(HPV) have a higher risk of developing cervical cancer if they have taken birth control pills for more than five years, according to a study conducted by the International Agency for Research on Cancer, an arm of the World Health Organization.

The study supports what many gynecologists have long suspected: that there is a causal connection between the pills and cervical cancer.

Nearly all sexually active women will be infected by HPV sometime during their lives, but in most cases the immune system quickly eliminates it. However, in some cases, the virus does not go away. If the infection persists, the chances of cancer increase enormously.

In this study, researchers pooled data from eight earlier studies of 3,769 women from four continents. Of those, 1,853 had cervical cancer, and 1,916 did not. Nearly all the women with cancer tested positive for HPV, while hardly any who were cancer-free had the virus.

The women who had taken the pill were no more likely than the others to be carriers of HPV, according to the WHO researchers. However, those infected with HPV who had used birth control pills for an accumulated total of five years or more were nearly three times as likely to develop cervical cancer as HPV-infected women who had never taken the pill. The increased risk persisted for up to 14 years after stopping the contraceptives.

Women who had taken the pill for 10 years or more were four times as likely to get the disease as those who had never taken it. Using the pill for less than five years did not result in a higher chance of cervical cancer.

So, based on the results from this study it seems logical to conclude that if you've got an HPV infection, oral contraceptives may actually be promoting the rate at which that progresses to cancer.

However, experts warned that the findings should be interpreted cautiously because the women were only tested for the virus once.